Quoted identifiers are confusing to many programmers, as they look similar to string literals. Moreover, for maximum portability, identifiers
should be self-descriptive and should not contain accents. Quoted identifiers can contain any character, which can be confusing.
Noncompliant code example
SET SERVEROUTPUT ON
DECLARE
  "x + y" PLS_INTEGER := 0; -- Noncompliant, quoted identifiers are confusing
  x PLS_INTEGER := 40;
  y PLS_INTEGER := 2;
  "hello" VARCHAR2(42) := 'world';  -- Noncompliant
BEGIN
  DBMS_OUTPUT.PUT_LINE("x + y"); -- Noncompliant, displays 0
  DBMS_OUTPUT.PUT_LINE("hello"); -- Noncompliant, confusing, displays "world" and not "hello"
END;
/
Compliant solution
SET SERVEROUTPUT ON
DECLARE
  my_int PLS_INTEGER := 0;
  x PLS_INTEGER := 40;
  y PLS_INTEGER := 2;
  greeting VARCHAR2(42) := 'hello';
BEGIN
  DBMS_OUTPUT.PUT_LINE(my_int);
  DBMS_OUTPUT.PUT_LINE(x + y); -- Compliant, displays 42
  DBMS_OUTPUT.PUT_LINE(greeting);
END;
/